Cellular base station antennas are known in the art, and known base station antennas are typically one of two types: (1) a printed circuit board and cables type base station antenna or (2) an airstrip line base station antenna. Both types present disadvantages.
First, the main disadvantage for a printed circuit board and cables type of base station antenna is cost. For example, the materials for the printed circuit board and for the cables are expensive and have a high insertion loss compared to an air dielectric. Furthermore, these types of antennas include numerous cable to printed circuit board solder joints as well as printed circuit board to printed circuit board solder joints. The number of solder joints adds to the cost of the antenna and increases the risk of passive inter-modulation (PIM) failures.
Next, the main disadvantages for an airstrip line type of base station antenna are performance and size. For example, radiation from the airstrip bends and loops is prevalent. Furthermore, there is a need for significant separation between the airstrips to avoid coupling between the airstrips. However, the separation between the airstrips causes increased bulkiness of the base station antenna.
In view of the above, it would be advantageous to combine a printed circuit board microstrip and airstrip in a base station antenna. For example, phase shifters and filters can be disposed on the printed circuit board, and straight feed lines and radiators can be made with the airstrip. However, there remains a continuing, ongoing need for a printed circuit board to airstrip transition that solves the problems discussed above.